Electromagnetic vibrating device



Jupe 611933. H. GRElBAcH 1,913,318

n ELECTROMAGNETIC VIBRATING DEVICE Filed June 21. 1950 ZSheets-Sheet 1 Ticl.

. glNv'laN-ron June 6, 1933. E. H. GREIBACH ELECTBOMAGNETIG VIBRATING DEVIC'E Fi1ed June 2l. 1950 2 Sheets-Sheet 2 mw my ,A w

ATTORNEY l Patented June e, 1933 UNITED STATES PATENT OFFICE a EMIL H. GREIBACH, OF NEW YORK,v N. Y., ASSIGNORTO SONOTONE ,CORPORATIONQ OF i NEWYQRK, N. Y., A. CORPORATION OF NEW YORK ELECTROMAGNETIC VIBRATING DEVICE Application ined Jane 21,

This invention relates to magneto electric vibrating devices, and more particularly to telephone receivers. y

`The invention has been made especially with the idea of providing a telephone `receiver foruse *as-the earphone` of a hearing aid device. Earphones, or earpieces, forming part of such devicesffor use by deaf people are desirably made as small andinconspicuous as possible, and a special object of the present invention is to secure in a receiver to be used for this purpose high electrical efliciency combined with` the utmost economy in space occupied. The invention i is, however, not limited `in its use to ear` phones, ibut is applicable to telephone re ceivers generally and to other vibrating devices in which the vibratory armature of the device does work otherthan the production of sound. Telephone receivers as commonly heretoforemade comprisea permanent magnet, usually of horseshoe or `Ufform, with coils placed around thelegs or polepieces of the y magnet, these coils being connected to a source of audio frequency current. The field of the permanent magnet in combination with the variable alternating `field produced by the coils furnishes the force which actuates the diaphragm. 'The usefulpart of this force is proportional to the product of the two flux densities, that is, the density of the permanent flux and that of the variable flux. As the path of the alternating flux is through the permanent magnet itself, and as the A. C. reluctance of the permanent magnet and the saturated pole pieces is relatively y high, the efficiency is necessarily low. And 40 iifurthermore, because of the magnet having to carry the variable flux produced by the coil, it has not been practicable to make the magnet of steel of the highest coercive force and correspondingly low permeability, and the practice has been to compromise by using y steels which do not give the highest'magneto motive force but which have a `better permeability, thus sacrificing some of the possible inagnetomoti've force to be furnished 'by the magnet in order to get a suit- 1930. semi No. 462,907,

able result from the flux produced by the variable current in the coil.

I have largely increasedthe effective vibromotive force of devices of the kind referred to and reduced the size of the device by providing in combination with a permanent magnet a separate path of low reluctance for the alternating lux,the construction being such that the alternating flux has a separate path of high permeability and is mixed with the permanent flux only at and near the narrow, interpolar air gap, that is, at the place where it has to produce the useful force. By such construction, not only is a more efficient use madeof the energizing current traversing thecoil, but it is possible to use magnets made of material, such as cobalt steel, having an extremely high coercive force and which furnish a very high magneto motive force..` y

A telephone receiver according to the invention in the form I now consider best comprises two U-shaped permanent magnets which are placed in line with the legs of the saine polarity adjacent each other, and a double U, or E-shaped, `core member of soft iron or `other suitable metal of high permeability which is placed to extend in a direction transverse to the permanent magnets and with its intermediate leg between the adjacent legs of the permanent magnets, the twoinner legs of the permanent magnets and the intermediate leg of this member combined forming a central leg or core the upper end of which serves as a ,common pole piece.

An energizing coil is placed around this central leg and pole piece, and the otherV pole piece of the magnets is provided by a plate,

and air gap. The construction provides substantially separate metallic paths ot different magnetic characteristics Jfor the variable and the permanent fluxes and permits the use of the most desirable materials for each, and thereby greatly increases the eliiciency of the device, and at the same time conserves space, so that the vibromotive force is high relatively to the space occupied.

The accompanying drawings illustrate a telephone receiver embodying the invention in the form I now consider best- The particular device shown is intended for use as the earphone of a hearing aid apparatus. Such earphones are commonly made in two general forms, one having a flat cover piece or cap substantially as shown in the drawings Jfor application to the outside of the users ear, and the other being a smaller iiistrument intended to be inserted into, or a partthereof inserted into, the aural cavity of the ear. In this smaller type, the instrument is necessarily more compact and has smaller parts. I have selected an .instrument of the larger kind for clearness of illustration, and the drawings are considerably enlarged from the actual size of the instrument. In said drawings: Y

' Fig. 1 is a broken plan view of telephone receiver embodying the invention;

Fig. 2 is a transverse sectional view taken on the line 2-2 of Fig. 1;

'Fig 3 isa similar view taken on the line 3 3 ot Fig. 1, at right angles to Fig. 2;

Fig. 4 is a sectional view in plan taken on the line 4-4 ot Fig. 2;

Fig. 5 is a plan view of a plate constituting a common pole piece;

Figs. 6 and 7 are side views of the member providing the variable magnetic circuit and of one of the permanent magnets, respectively Fig. 8 is a cross sectional view of the diaphragm member; and

Fig. 9 is a side view of a modified divided form of the member shown in Fig. 6.

Referring to the drawings, the operative parts of the receiver are mounted within a casing comprising a cup-shaped housing 10 and a cap piece 11 which screws on to the exteriorly threaded end of the housing and is of a diameter to tit against the ear of the wearer and is provided with a central opening 12 for the escape of sound waves from the diaphragm ot the instrument.

Seated within the housing 10 are vtwo U- shaped permanent magnets 15 arranged in line diametrically across the housing chamber withtlieir legs of like polarity adjacent each other. A double U-, or E-shaped, core member 16 of sott ii'on or other metal of high permeability extends diametrically across the housing chamber between and at right angles to the magnets 15. The magnets 15 are thus arranged symmetrically one on each side of the core member 16, with the intermediate leg 17 of the member 16 between the inner legs of the magnet 15 so as to form collectively a central core the upper end of which serves as a common pole piece 18 for themagnets 15 and core member 16. The magnets 15 and the two ends of the core ineinbei 16 thus radiate from the central Vpole piece 18. The position of the intermediate leg `of the core member with relation to the two permanent magnets is such as to avoid saturation of the leg by the permanent lux. VThis is important, since it' so saturated the leg would have a relatively high reluctance.

An energizing winding or coil 2O extends about the central core and pole piece between it and the outer legs of the magnet and core member. The coil is mounted on a spool 21 of insulating material, and the ends of the coil are connected to contact terminals 22 which. when the spool is placed in position engage the inner ends of bushings or sockets 23 set in the wall of the housing 10 and adapted to receive connecting terminals of conductors for supplying the energizing current to the coil.

Another common pole piece is formed by a plate or disc 30, preferably of sott iron or other metal of suitably high permeability, having a central opening 31 somewhat larger than the end of the pole piece 18 and openings or notches 32, 32 and 33, 33 to receive the ends of the outer legs of the magnet 15 and ot the core member 16. This pole plate is set over the coil with the ends of the outer legs of the magnetand core member in the notches 32 and 33 and with the end of the pole piece 18 extending into the central opening 31 to form therebetween a common air gap 34 for the several magnetic circuits. This interpolar air-gap, as shown at 34 is narrow, being not much greater-than twice the width of the air-gap between the armature and the pole pieces. The diaphragm member 40 mounted over the plate 30 may be of any suitable construction. As shown, it comprises a thin metal diaphragm carried by a peripheral ring 41 and provided with a central thicker portion 42 to serve as the armature. The armature extends over the pole piece 18 and air gap 34 and partly over the plate 30 so as to bridge over the air gap and be in the combined flux field.

In order to accommodate the diaphragm ring 41,'the plate 30 is near its periphery flanged downwardly and then outwardly, its outwardly extending flange 43 seating on a shoulder 44 in the side ot the housing, and providing aseat for the diaphragm ring 41, spacing rings 45 being used to secure the desired positioning of the pole plate and the diaphragm with relation to each other and to the pole 18. To reduce eddy currents, the plate 30 has a slot 46a extending inward from one of` the notches 33 to thelcentral opening 31. Slots 46 extend from the other `30 surroundingthe end of the pole piece 18 contributesmaterially to the economy of space 1n the receiver.`

. `lVhen an energizing current is supplied to the coil, the alternating flux produced bythe coil linds two pathsV ci' low` reluctance through thecentralpole piece 18, each radiating portion of the core member 16,a por-` tion of the pole plate 30,:air Vgap 34 and the armature, and most of the alternating flux takes these paths. Only very small portion ofthe alternating flux passes through the permanent magnets because of their high Al C. reluctance. At the same time the flux of the permanent magnets is flowing in paths consisting each of the central pole piece, one of the magnets l5, a portion of the pole piece 30,`air gap 34 and the armature. A partlof o the permanent flux will be lost over the shunt path from thecenter legs oh the permanent magnet to the center portionsof` the soft iron cores 16, then through the soft iron cores to the pole piece 30 and therethrough tothe outer legs of the permanent magnets. The junctions between the outer ends of the soft iron cores and the pole pieces form points ot" relatively high reluctance, due to the notches atSB, so that this shunt flux-is held down within limits at which the permanent as welles the induced fluxes passing through the air-ga`p have the most `favorable values. Thereare thus provided two complete 1nagnetic fcircuits for the permanent magnetic flux and twocomplete magnetic circuits `for the variable flux, andthe variable flux circuits are separatefrom the `permanent flux circuits except where they join at the common pole pieces and the air gap and the ar` The two fluxes thus have for the mature. y most part separate paths, being combined7 however, at the `place `where they contribute to the production of the useful force. It is thus possible to use permanent magnets of `material having very high coercive force,

such as cobalt steel, which because of their extremely low permeability are not suitable for use when they have to carry alternating liux.

l The area of the central pole piece may by beveling off theends of the inner legs oli the permanent magnets be madeas small as desii-able for securing the greatest torce on the armature, the `area being desirably smaller as the thickness of the armature is less. this way thorough superimposition and intermingling of the permanent and induced fluxes at the point ofaction on `the armature is Obtained. This intermingling of the fluxes may be further increased vby making the end of the intermediateleg of the soft iron core member protrude somewhat beyond the ends InV of the legs of the permanent `magnets to furnish the entire effective pole area, as shown, Jfor example, in Fig. `9.

It is to be understood that the invention is not limit-cd to the particular construction and arrangement of parts shown in the dra`wings and to which the foregoing description has been largely confined, but that it includes departures therefrom within the claims.

The use ot the terms A. C. and alternating7 as'applied to the tlux and to thecurrent fed to the coil is netto be taken as implyingthat devices according to the invention are useful only when the coil is supplied with a purely alternating current. The invention is also useful when supplied with what is commonly termed a pulsating current. Such a current may be considered as comprising a D. C. componentand anA. C. component. v

The two permanent magnets 15 form in ellect a double U magnet, and the E-shaped core member l@ forms with the coil a double U `variable magnet. Obviously, it is not necessary that the permanent rmagnet be made in two sepa-rate parts and the variable mag` net continuous :trom end to end, and the invention is not inits broader aspect limited to this construction. I consider it more desirable, however', to have it so, rather than to make the double U permanent magnet continuous and the variable magnet, or core member in tivo separate parts, as shown, for example, in Fig. 9. y

Nor is the invention considered broadly limited to a single coil device having a d0u ble U permanent magnet and a double U variable magnet core member combined totorm a single central commoncore and pole piece about which the single coil islplaced. A two y coil receiver according to the invention might for example have two E-shaped core mem#` bers combined With three U-shaped permanent magnets, or with one U-shaped permanet magnet, to form two common poles, one for each coil.

What is claimed is:

l. A vibrator, coi'nprising a plurality of permanent magnets of U shape, and a variable magnet having an E-shaped core member 0l. metal of high magnetic permeability, legs of said permanent magnets of like polar- `ity being disposed on opposite sides of the intermediate leg of `said core member to constitute a common pole piece.

2. A vibrator, comprising a plurality of permanent magnets otU shape, an E-shaped core member of metal of higlrmagnetic permeability, legs of like polarity of said pernianent magnets being disposed on opposite sides of the intermediate leg of said core member to constitute a common pole piece, `a coil surrounding said common pole piece, and a plate forming another common pole piece havinganopening and positioned to provide a common air gap between the edge of said opening and the first said pole piece and extending outward to the outer legs of said magnet and core member.

3. A vibrator, comprising a double U permanent magnetic structure of metal of high coercive force, a double U magnetic core of metal ot' high magnetic pern'ieability, said magnetic structure and core extending transversely of each other and their` inner legs forming a common pole piece, a coil between said pole piece and the outer legs of the niagnetic structure and core, means providing a second pole piece forming an air gap about the end of the first said pole piece and extending outward to said outer legs, and a \'f'ibratory armature mounted adjacent to said pole Vpieces and extending over the air gap.

4. A vibrator, comprising a double U permanent magnetic structure of metal of high coercive force, a coil mounted between the inner and the outer legs of said magnetic structure, means providing a path of low A. C. reluctance for flux produced by said coil, and an armature rvibrated by changes V1n the iiux produced by said coil.

5. A vibrator, comprising flux paths for separate permanent and variable magnetic circuits, the permanent magnetic circuits being formed of high reluctance material and the variable magnetic circuits being formed of low reluctance material, both the permanent and Variable magnetic circuits extending radially in a common plane from a common pole piece formed byportions thereof and an armature adjacent to said plane for vibration in a direction perpendicular thereto.

6. A vibrator, comprising means providing a plurality of flux paths terminating in a central common pole piece, a plate having a central opening and overlying said means and forming an air gap about said pole piece, and a vibratory. armature mounted outside of but adjacent to said air gap.

7. A vibrator, comprising both permanent and alternating current magnets having legs terminating in substantially a single plane, certain legs of said magnets constituting a common pole piece, and a metallic member lyinO' in substantially the plane of the ends of said legs and being connected to legs of said magnets to form a second common pole piece and forming an air gap with the first-named common pole piece.

8. A telephone receiver, comprising a permanent magnet having legs, a separate variable magnet having legs, juxtaposed legs of sain magnets constituting a. common pole piece. a metallic member engaging other legs ot said magnets and forming an air gap about said common pole, and a diaphragm member providing an actuating armature positioned in the combined flux fields of said magnets at said air gap.

9. A telephone receiver, comprising two U-shaped permanent magnets set in line with their legs of like polarity adjacent each other, an E-shaped core member of metal of high magnetic permeability set at right angles to the permanent magnets with its intermediate leg between the inner legs of the permanent magnets, the inner legs of the permanent magnets and the intermediate leg oi the core member combined forming a central core and pole piece, a coil surrounding said central core and pole piece, a plate of metal of high magnetic permeability set over said coil having a central opening to receive the end of the central pole piece and to define an air gap therewith and having openings to receive the'ends of the outer legs of the permanent magnet and the core member, and a diaphragm member providing an actuating armature positioned in the combined flux field ot said magnets and said core member at the air gap. i

l0. A vibrator comprising a vibratory armature, two separate magnetic circuits on one side of said armature, one circuit including a permanent magnet of relatively low magnetic permeability while the other circuit includes an electromagnet having a core of relatively high magnetic permeability, and both of said circuits consisting substantially Wholly of magnetic material except for a relatively narrow air-gap substantially parallel to but adjacent said armature and having substantially parallel adjacent portions extending through the coil of the electro-magnet in a general perpendicular direction toward the central part of said armature, whereby the flux through the armature is a mixture of the fluxes produced by the permanent magnet and the electromagnet.

ll. A vibrator comprising a vibratory armature, a winding disposed on one side of said armature, a core within said winding, having its upper end adjacent said armature and comprising a permanently magnetized part of relatively low magnetic permeability and a non permanently inagnetized part ot relatively high magnetic permeability, adapted to form an electromagnet when a current flows through said winding, whereby the flux through the armature is a mixture of the fluxes produced by the permanent magnet and the electromagnet, and magnetic material extending from the lower ends of said core upwardly around said winding and inwardly to within a short distance from the upper ends of said parts to provide magnetic circuits consisting substantially wholly of magnetic material except for relatively narrow air-gap adjacent said armature.

12. A vibrator comprising a circular vibratory magnetically operated diaphragm, means for producing a flow of magnetic flux substantially along the axis of vibration of Cil ,to but adjacent said diaphragm, then away Yfrom the diaphragm adjacent the periphery thereof and iinally radially inwards, said means including both a permanentmagnet `and an electromagnet whereby the flux operating the diaphragm is a mixture of the fluxes produced by the permanent magnet and the electroni agnet.

`13. An electromagnetic vibrator, comprising an inducing coil adapted to betraversed `by alternating current, a permanent magnet l 15 core `extending through said coil, a shunt core of non-retentive, highly permeable mag netic material providing a relatively low reluctance path for variable flux induced by said coil, commonpole pieces for said cores forming a gap for the fluxes passing through said cores so that the permanent lux of one core and the induced alternating fluxes of the othercore enter the gap substantially superimposed and intermingled, with the permanent linx predominating the induced flux in the gap, and a member actuated'by the variations of the intermingled iux in said gap.

14. An electromagnetic vibrator, comprising an inducing coil, an inner'core member extending through said coil and having at one end a central pole piece, a plurality of permanently magnetized core members extending from the opposite end of the inner core member around said coil, a highly permeable non-retentive magnetic` core shunting said permanent magnet coremembers .to provide a relatively low reluctance path for variable flux induced bysaid coil, said co-re members having a common polepiece forming with said central pole piece a gap, said pole pieces and said coresbeing so arranged that the permanent iiuxesand theinduced alternating fluxes of said cores enter the gap substantially superimposed and intermingled, with the permanent iux predominating the induced flux inthe gap and a member actuated bythe variations of the intermingled flux in said gap. l

15. An electromagnetic vibrator, comprising an inducing coil, an inner core member extending through said coil and having at one end `a central pole piece, a plurality of permanently magnetized core members radially extending from the opposite end of the inner core member around said coil, highly permeable non-retentive magnetic core members shunting said permanent magnetcore members to provide a relatively low reluctance path for variable iiux induced by said coil, said core members having a common pole piece forming with said central pole ieee `a a said ole ieces and said core members being so arranged that the permanent fluxes and the induced alternating fluxes of said core members enter the gap substantially superimposed and intermingled, with the permanent flux predominating the induced flux in the gap and a member actu-ated by the variations of the intermingled flux in said gap. a

16. An electromagnetic vibrator, comprising an inducing coil adapted to be traversed by alternating current, an inner core portion extendingthrough said coil and having at one end a pole piece, said inner core portion comprising a permanently magnetized core member and a non-retentive highly permeV- able core member united at said pole piece so that the permanent linx of one member is superimposed and intermingled at the pole piece with induced alternating flux in the other core member, a second pole piece forming a gap with said first pole piece and so joined to the other ends of said core members that the permanent and alternating iiuxes of the core members enter into the gap superimposed and intermingled, with the permanent flux predominating the induced flux and a member actuated by the variations of the intermingled flux in said gap.

17. An electromagnetic vibrator, comprising an inducing coil adapted to betraversed by alternating current, an inner core portion extending through said coil and having at one end a pole piece, said inner core comprising a permanently magnetized core member and a non-retentivehighly permeable core member unitedat said pole piece so that the permanent iiux of one member is superimposed and intermingled at the pole piece with induced alternating flux in the other core member, outer permanently magnetized and non-retentive core members extending from the other ends of said inner permanently magnetized` andnon-retentive core members, respectively, around saidcoil, a second pole piece forming a gap with said first pole piece and so joined to the outer ends of said outer core members that the permanent and alternating `fluxes of the core members enter into the gap superimposed and intermingled with the permanent flux predominating the induced flux, and a member actuated by the variations of the intermingled flux in said sar- 1 y In testimony whereof I have hereunto set my hand.

EMIL H. GREIBACH.

CERTIFICATE OF CORRECTION.

APatent No. 1,913,318. June 6, 1933.

EMIL GREIBACH.

It is hereby certified that error appears in the prinre specification of the above numbered patent 'requiring corrootion as follows: Page a, lines 67 and 68, strike out the comma and words as shown, for example, ir. Fig. 9"; and that thewsaid Letters Patent should be read wiih this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 13th day oiNovember, A. D. 1934.

Les I ie Frazer (Seal) Acting Commissioner of Patents. 

